Method and apparatuses for measuring and correcting the stress profile of saw blades

ABSTRACT

A saw blade (10), in particular for band saws, is moved through a measuring path and a rolling path in a direction of travel (A) which essentially corresponds to its longitudinal direction, with two marginal regions of the saw blade (10) being supported on the measuring path-and held down in a start portion and an end portion of same and thus being held in a common reference plane which contains the direction of travel (A) and the saw blade (10) being lifted above the reference plane by a supporting force which is exerted only in the central area of the measuring path. The profile of the saw blade (10) is then measured in a measuring plane (B) which extends orthogonally to its direction of travel (A) in the center area of the measuring path, with data of the profile height relative to a chord which extends transversely to the direction of travel (A), coordinated with data of the distance of the measuring points from an edge (14) of the saw blade (10) and data of the longitudinal movement of the saw blade is stored. The saw blade (10) will be rolled in the direction of travel (A) region-by-region in accordance with this data.

The invention relates to a method for measuring and correcting thestress profile of an elongated saw blade, in particular for band saws,wherein

the saw blade is moved through a measuring path and a rolling path in adirection of travel which essentially corresponds to its longitudinaldirection;

two marginal regions of the saw blade are supported on the measuringpath and held down in a start portion and an end portion of same;

the profile of the saw blade is measured in the central area of themeasuring path in a measuring plane which is orthogonal to its directionof travel;

data of the profile height relative to a chord which extendstransversely to the direction of travel, coordinated with data of thedistance of the measuring points from an edge of the saw blade and dataof the longitudinal movement of the saw blade is stored; and

the saw blade is rolled in the rolling path in a region-by-region mannerin the direction of travel in accordance with this data.

The invention further relates to an apparatus for carrying out such amethod, comprising

a machine table on which an elongated saw blade, in particular for aband saw, is movable in a direction which essentially corresponds to itslongitudinal direction;

a measuring station arranged at the machine table, comprising

a measuring plane which extends orthogonally to the direction of traveland in which at least one sensor is arranged;

one pair of parallel blade supports for one edge region each of the sawblade; and

two pairs of holding-down devices which are arranged in a start and anend zone, respectively, of the measuring station for pressing the sawblade onto the blade supports symmetrically to the measuring plane.

A method and an apparatus of this generic type are known from AT-B-342385(equivalent of U.S. Pat. No. 3,919,900 to Allen et al.) There, anendless saw blade for a band saw runs over two deflection rollers whichare supported in a machine frame so as to be rotatable about ahorizontal axis each and limit an area of the machine frame in betweenwhich in the following--and also with reference to the presentinvention--will be designated as the machine table. On the machinetable, several stations are arranged in series in the direction oftravel of the saw blade which are required for measuring and correctingthe stress profile and the curvature of the saw blade back, i.e. ameasuring station for sensing the blade back, a measuring station forsensing the stress profile and a rolling station for correcting thestress profile and the curvature of the back of the saw blade.

Here and in the following the term blade back of a single-sided toothedsaw blade refers to the edge opposite the toothed edge. This, however,is not be be construed as excluding saw blades with teeth on both sidesfor band saws and gate saws--also in the context of the presentinvention; in the case of such saw blades one of the two toothed edgesis sensed instead of a smooth edge in order to determine whether and howthe saw blade is curved in its plane and whether it deviates from itsintended direction of travel.

The measuring station for sensing the blade back of the mentioned knownapparatus comprises two skid-type guides which, relative to thedirection of travel of the saw blade, are arranged at a distance onebehind the other and define a vertical contact plane for the blade back.A sensor is arranged between these two guides which senses the bladeback in the plane of the saw blade orthogonally to its direction oftravel. On the basis of the data determined in this manner, the radiusof curvature can be calculated for any position of the blade back.

Relative to the direction of travel of the saw blade, the measuringstation for sensing the stress profile is arranged at a distance behindthe measuring station for sensing the blade back, and comprises twoformed plates with arc-shaped upper edges which are arranged parallel tothe direction of travel of the saw blade in one vertical plane each andsupport same in one marginal region each, so that they define ameasuring path. In a start area and an end area of this measuring path,one pair of poles each is fastened at the machine frame, and aholding-down arm is hinged at the upper end of each pole for pivoting ina vertical longitudinal plane, at the bottom end of which a holding-downroller is supported. The total of four holding-down rollers press thesaw blade against the two formed plates in the start and end area of themeasuring path. Magnets are arranged along the upper edges of the formedplates, which prevent the saw blade from developing bulges instead ofmoulding itself in the intended manner to arc-shaped upper edges of theformed plates and to slide along them. The saw blade in this measuringpath is thus forced to adopt a curvature which is established by theformed plates which can only be changed by replacing the formed platesby differently formed ones. In a vertical central plane of the measuringpath, a sensor is arranged so as to transversely move the saw blade toand fro in order to measure its stress profile.

The reasons for the occurrence of the stress profile and the principlesof correcting same by rolling are known; in this context, reference ismade for example to DE-A-42 14 784 in addition to AT-B-342 385 mentionedabove.

According to AT-B-342 385 the saw blade eventually travels through arolling station which is also arranged on the machine table and whichcomprises a roll pair which can be adjusted transversely to the sawblade and subjected to a hydraulic pressure in order to deformingly actupon selectable regions of the saw blade and thus correct its stressprofile. The apparatus known from DE-A-42 14 744 also comprises amachine table which is arranged between two deflection rollers overwhich a saw blade travels on which several measuring paths are arrangedone behind, the other in the direction of travel of the saw blade, i.e.a measuring path for the stress profile, a travel measuring path andmeasuring path for bulges and dents. The measuring path for the stressprofile is arranged in an area in which the saw blade is curved as aresult of its deflection My one of the deflection rollers so that itreveals its stress profile automatically without having to be liftedfirst. Downstream of the latter measuring path, the measuring path forbulges and dents, a processing unit is arranged which comprises severalroll pairs, i.e. one for leveling out bulges, one for leveling out dentsand one for correcting the stress profile of the saw blade.

The invention is based on the object (if simplifying measuring andcorrecting the stress profile of an elongated saw blade and, ifrequired, of simplifying the elimination of bulges and dents, which isbriefly referred to as leveling, under process and apparatus engineeringaspects.

According to the invention, the object is solved by a method of theinitially mentioned generic type in that

the marginal regions of the saw blade are retained in the start area andthe end area of the measuring path in a common reference plane whichincludes the direction of travel;

the saw blade is lifted above the reference plane by a supporting forcewhich is exerted only in the central area of the measuring path; and

the stress profile developed in this manner is measured.

As far as it concerns an apparatus, the mentioned object is solvedaccording to the invention and based on an apparatus of the initiallymentioned generic type in that the pairs of holding-down devices,remaining disposed symmetrically with the measuring plane, areadjustable in and opposite, respectively, to the direction of travel ofthe saw blade so as to approach each other or to retreat from eachother.

This enables saw blades of widely different widths and thicknesses to bemeasured in brief succession and their stress profile to be correctedwithout necessitating time-consuming retrofitting operations.

The conversion to saw blades with different widths and thicknesses, i.e.also with a different rigidity, is particularly facilitated when thesupporting force is exerted in the measuring plane only and therepreferably only at a distance from the two marginal regions in such aregion where the maximum profile height is to be expected. Theadaptation to saw blades of different rigidity is further preferablyfacilitated in that the holding-down forces are exerted on the marginalregions of the saw blade only at variable identical distancescorresponding to the width and thickness of the saw blade upstream anddownstream the measuring plane. The design means for achieving thisadaptability are of an extremely simple design and can be handledeasily.

Saw blades of different widths and thicknesses often have very differenttendencies to deviate from the intended route of travel depending of thestresses to which they are subjected during operation. In this respect,too, the described known method is hard to carry out with certain sawblades and it is not easy to operate the associated apparatus. In orderto simplify the measurement and correction of the stress profile of anelongated saw blade, which may be a saw blade of a band saw or a gatesaw, in this respect, too, deviations from a given position which aredetermined on one edge of the saw blade are corrected according to theinvention by rolling the saw blade in accordance with these deviationsin a direction more or less slanted relative to its longitudinaldirection. This is done by means of a roll pair which according to theinvention can be adjusted so as to be slanted in accordance with themeasuring data of at least one measuring station which senses the edgeof the saw blade.

In the following, an embodiment of the invention will be described inmore detail with reference to the drawings, in which:

FIG. 1 is an isometric view of the major portion of a machine accordingto the invention for leveling saw blades;

FIG. 2 shows an enlarged still more schematic section from FIG. 1;

FIG. 3 is the front view of the entire machine;

FIG. 4 is the plan view associated with FIG. 3;

FIG. 5 is the front view of the main portion of the machine drawn to alarger scale;

FIG. 6 is the plan view associated with FIG. 5;

FIG. 7 is a further enlarged front view of an assembly from FIG. 5;

FIG. 8 is a rear view corresponding to FIG. 7;

FIG. 9 is a further enlarged longitudinal view in the direction ofarrows IX--IX in FIG. 5;

FIG. 10 shows an enlarged section in plane X of FIG. 5;

FIG. 11 is an enlarged section from FIG. 5;

FIG. 12 shows an assembly from FIG. 6 in an enlarged horizontal section;

FIG. 13 shows another assembly from FIG. 6, also as an enlargedhorizontal section; and

FIG. 14 shows the section XIV--XIV in FIG. 13.

The illustrated machine serves to automatically level saw blades 10. Theillustration shows a band saw blade which has teeth 12 along alongitudinal side and a smooth blade back 14 at the oppositelongitudinal side; it is, however, possible to process band saw bladeswith two-sided toothing as well as gate saw blades. The machine has anelongated machine table 16, at the two face ends of which one frame 18each is installed as an extension. At the frames 18, horizontal guiderolls 20 are supported parallel to each other at an adjustable distancefrom the machine table 16. The saw blade 10 travels in the direction ofarrow A in FIGS. 1 to 3 over the guide rolls 20 at the left frame 18 andsubsequently through several stations arranged on the machine table 16,i.e. a measuring station 22 which senses the surface of the saw blade 10in a vertical direction, a leveling station 24 for leveling bulges anddents in the saw blade 10, a rolling station 26 for driving the sawblade 10 and providing it with a desired stress profile, at least onemeasuring station 28 which senses the blade back 14 in a horizontaldirection transverse to its direction of travel, and via further guiderolls 20 at the machine table 16 and the right frame 18. The saw blade10 can also be moved in the opposite direction of the arrow A. In theillustrated example three measuring stations 28 for sensing the bladeback 14 are arranged over the entire length of the machine table 16.Said stations and guide rolls 20 are shown in more detail in FIGS. 7 to12 or in FIGS. 13 and 14, respectively, and will be described in thefollowing.

Columns 30 are associated with the measuring station 22 and are fastenedto the machine table 16, at the left-hand side of which (FIG. 9) astationary, horizontal rear blade support 32 in the form of alongitudinal hardened and ground steel strip is arranged. A longitudinalguide 34 is fastened parallel to it at the rear side of the column 30,at which two rear holding-down devices 36 are arranged so as to beadjustable symmetrically to a vertical plane which extends transverselyto the longitudinal direction of the machine table 16 and which will bereferred to in the following as measuring plane B. In addition, twotransverse guides 38 are fastened on the machine table 16, in which onecross slide 40 each is adjustably guided. The two cross slides 40 carrya front horizontal blade support 42 which also extends in thelongitudinal direction of the machine, i.e. parallel to the rear bladesupport 32, and which is also formed by a strip from hardened and groundsteel. The surfaces of the two blade supports 32 and 42 lie in a commonhorizontal plane so that the saw blade, as long as it rests upon them,is held horizontally. A front longitudinal guide 44 is also fastened toboth cross slides 40, at which two front holding-down devices 46 areadjustably arranged symmetrically to the measuring plane B.

A supporting means 48 (FIGS. 6 and 9) is also associated with themeasuring station 22, the purpose of which is to support the saw blade10 in the measuring plane B in the area between the two blade supports32 and 42 and at approximately the same distance from the rear bladesupport 32 as from the front blade support 42 in approximately onesingle point, as will be described below in more detail. The two crossslides 40 are adjustable along the transverse guides 38 by means of ascrew spindle 50 (FIG. 6) which is supported in parallel thereto on themachine table 16 in an axially stationary manner. The screw spindle 50can be rotated by means of a handwheel 52 (FIGS. 3, 5 and 9) and iscoupled with a reduction ratio of 2:1 to a similar screw spindle 54which extends parallel to it and meshes with the supporting means 48.Rotating the handwheel 52 makes it possible to adjust the distance ofthe transversely adjustable front blade support 42 and the holding-downdevices 46 from the stationary rear blade support 32 together with theassociated holding-down devices 36 to the width of the saw blade to beprocessed; at the same time, the supporting means 48 is adjusted alonganother horizontal transverse guide 55 (FIGS. 5 and 6) in such a mannerthat its distance ratios with respect to the two blade supports 32 and42 remain constant.

At the left end of the machine table 16 (FIGS. 1 to 6) a stationaryholding-down device 56 is arranged at the rear side facing away from aviewer of FIGS. 1, 3 and 5, and a holding-down device 58 is arranged atthe front which is connected with the two cross slides 40 for a commontransverse movement, i.e. which is also adjustable corresponding to thewidth of the saw blade 10.

The holding-down devices 36 and 46 which are arranged symmetrically withthe measuring plane B are shown in the drawings in a position where theyhave the smallest possible distance from the measuring plane B. Thisposition serves to measure particularly narrow and thin saw blades 10.From the illustrated position, the two rear holding-down devices 36 andsimilarly the two front holding-down devices 46 can be adjusted so as toretreat from one another in the direction of the double arrows C in FIG.5, with their arrangement remaining symmetric to the measuring plane B.The circles shown in broken lines in FIG. 5 indicate the positions inwhich the holding-down devices 36 and 46 assume their largest possibledistance from the measuring plane B. This position is intended formeasuring particularly wide and thick saw blades.

In order to adjust the holding-down devices 36 and 46 in thelongitudinal direction of the machine table 16, a drive 60 (FIGS. 3, 4and 8) is provided which in the illustrated example is a hydraulicpiston/cylinder unit with a piston rod 62, the end of which beingfastened to one of the two rear holding-down devices 36. In order toensure that the rear holding-down devices 36 and correspondingly thefront holding-down devices 46 are always moved symmetrically to themeasuring plane B, at the front and rear side of the machine table 16one toothed belt 64 each is guided in a vertical longitudinal plane overtwo deflection gears 66. The deflection gears 66 which are arranged atthe front and rear side of the machine table 16 are in synchronism witheach other by means of shafts 68 (FIGS. 7 to 9). One of the two rearholding-down devices 36 is rigidly connected with the upper half of therear toothed belt 64, and the other is connected with the lower half ofthe rear toothed belt 64, and in a corresponding manner one of the twofront holding-down devices 46 is connected with the upper half of thefront toothed belt 64 and the other is connected with the lower half ofthe front toothed belt 64. The deflection gears 66 of the rear toothedbelt are rigidly mounted on the shafts 68; the deflection gears 66 ofthe front toothed belt 64, however, are slidably guided axially onmultiple splined profiles of the two shafts 68 so that the front toothedbelt 64 can participate in transverse adjustments of the two frontholding-down devices 46.

All holding down-devices 36, 46, 56 and 58 are of an essentially similardesign. They have a pivot arm 70 (FIG. 9) each which can be swivelledabout a horizontal longitudinal axis D. Each of the rear holding-downdevices 36 and 56 is equipped with a hydraulic piston/cylinder unit 72for swivelling its pivot arm 70. Each of the front holding-down devices46 and 48 is provided with a locking handle 74 by means of which theassociated pivot arm 70 can be manually swivelled between the openedposition indicated by broken lines in FIG. 9 and the closed positionindicated by solid lines and locked in the closed position. At the endof each pivot arm 70 a guide rod 76 is supported so as to be pivotableabout a horizontal transverse axis E and is biased by a spring 78 in thesense of a downwardly directed swivelling motion towards the closedposition. At the end of each guide rod 76 a holding-down roller 80 issupported so as to be rotatable about an axis which is parallel to thetransverse axis E. The holding-down rollers 80 of all holding-downdevices 36, 46, 56 and 58 are arranged vertically above the associatedblade support 32 or 42, respectively. In the closed position theholding-down rollers 80 subject the saw blade 10 to the bias generatedby the associated spring 78, which slidably rests on the blade supports32 and 42 with an area adjacent to its teeth 12 or its blade back 14.

The supporting means 48 (FIGS. 9 and 11) incorporates a supporting slide82 which is adjustable on the additional transverse guide 55 by means ofthe screw spindle 54 and which carries a supporting arm 84 (FIG. 11)which can be swivelled about a horizontal transverse axis F. At thesupporting arm 84 a supporting roller 86 with a spherical surface issupported so as to be rotatable about a horizontal axis G which isparallel to the transverse axis F and thus also extends transversely.Instead of or in addition to its spherical shape the supporting roller86 can be provided with an elastic coating. In each case, the edges ofthe supporting roller 86 must be prevented from impressing themselvesinto the saw blade 10. A lifting device 88 bears against the supportingslide 82, which in the illustrated example is a piston/cylinder unit,the piston rod of which being hinged at the end of the supporting arm84. By advancing the lifting device 88 the supporting arm 84 can beswivelled upwards from its rest position shown in FIG. 11; thisswivelling motion and thus the associated adjustment of the supportingroller 86 in an upward direction is limited by a stroke limiter 90 whichin the illustrated example is formed by a screw bolt.

Also associated with the measuring station 22 is an upright 92 (FIGS. 9and 10) which is fastened to the machine table 16 and on which ameasuring slide 94 is guided so as to be horizontally adjustable in themeasuring plane B. The two ends of a toothed belt 96 which runs viadeflection rollers 98 and a pinion 102, which can be driven by a motor100, e.g. a stepping motor, are fastened at the measuring slide 94. Themeasuring slide 94 has a front end which is arranged at the left side inFIGS. 9 and 10, at which an angle lever 104 is supported so as to bepivotable about a horizontal longitudinal axis H. The angle lever 104carries a first sensor 106 and is biased by a spring 108 which has thetendency to hold it in contact with an adjustable stop 110, by means ofwhich an operating position of the sensor 106 is defined. The sensor 106can be swivelled from the operating position into a rest position bymeans of an electromagnet 112 which is hinged at the angle lever 104. Inthe vicinity of the front end of the measuring slide 94 an additionalsecond sensor 114 is securely mounted. The first sensor 106 has, forexample, a measuring range of 1.5 mm and is capable of measuring bulgesand dents of the saw blade 10 with an accuracy of 0.01 mm. The secondsensor 114 has a measuring range which is larger by about one power often and serves to sense the stress profile of the saw blade 10.

The levelling station 24 per se is of known design and is therefore notshown in detail. It comprises a roll frame 116 which in a side view isC-shaped (FIGS. 1, 5 and 6) and which is adjustable on transverse guides118 fastened on the machine table 16. The roll frame 116 supports twolower stationary rolls 120 and two upper rolls 122 which are adjustablysupported by one eccentric arrangement each. By adjusting the upperrolls 122 by means of one actuator 124 each, e.g. by one hydraulicpiston/cylinder unit each, a rolling pressure can be applied to the sawblade 10 which is supported from below by the lower rolls 120. The axesof rotation of all rolls 120 and 122 extend horizontally andtransversely to the longitudinal direction of the machine table 16; therolls 120 and 122 are freely rotatable and have one conical shoulder 126each to facilitate the introduction of the saw blade 10 transversely tothe machine table 16 from the front to the rear between the rolls 120and 122.

Another pair of transverse guides 128 is fastened on the machine table16, on which a substructure 130 of the rolling station 26 is adjustablyguided. On the substructure 130 a roll frame 132 which is also C-shapedwhen viewed from the side (FIG. 1, 2, 5 and 6) is supported so as to bepivotable about a vertical axis J. In the roll frame 132 a lower roll134 and an upper roll 136 are supported so as to be rotatable abouthorizontal rotary axes W1 and W2 which are parallel to each other. Theupper roll 136 can be pressed by means of a contact pressure device 138,for example a hydraulic piston/cylinder unit, against the saw blade 10which is supported by the lower roll 134. The pivot axis J intersectsboth rotary axes W1 and W2 at approximately right angles and extendsthrough those points where the rolls 134 and 136 contact the saw blade10. In order to drive the rolls 134 and 136, the rolling station 26 isprovided with a motor 140. An actuator 142, for example a servo motor,is also associated with the rolling station 26, by means of which theroll frame 132 can be swivelled about the vertical axis J and be broughtfrom a central position in which the rolls 134 and 136 run in thelongitudinal direction of the machine table 11 into a controlled slantedposition so that the blade back 14 runs within a given tolerance rangealong the third of the three measuring stations 28 assigned to it. Tothis end, it is generally sufficient to swivel the roll frame by lessthan 1° from its central position to the one or the other side. Themaximum swivel range is preventively set to 3 ° in either side, i.e.amounts to a total of 6°.

Of the three measuring stations 28 which are assigned to the blade back14, the first one is arranged at the start, the second one is arrangednear the centre and the third one near the end of the machine table 16.The three measuring stations 28 are identical; one of them is shown inFIG. 12 as a horizontal section. It has a supporting beam 144 which isfastened at the machine table 16 and movably guides a horizontaltransverse rod 146 along its axis K. A measuring slide 148 is supportedat the rod 146 in the manner of a balance beam, but pivotable about avertical axis L. Two biased springs 150 attempt to hold the measuringslide 148 in a standard position in parallel to the longitudinaldirection of the machine table 16 (FIG. 12). The two springs 150 bearagainst the supporting beam 144 and are each guided on one bolt 152which is screwed into it. A distance sensor 154 is fastened at thesupporting beam 144, which continuously measures the position of a plate156 which is fastened at the rod 146 and thus the position of themeasuring slide 148.

A sensor 158 (FIG. 1) is further fastened at the machine table 16, whichemits a signal if a marking on the saw blade 10, for example a dashapplied with a felt-tip marker, travels past it. All signals emittedfrom the measuring station 22 by the sensors 106 and 114, as well as thesignals emitted by the three measuring stations 28 and the sensor 158are supplied to a central computing and controlling unit 160. The sameapplies to signals which indicate the position of the actuator 142 andthe revolutions of the rolls 134 and 136.

In addition to the guide rolls 20 which are supported on both frames 18,another guide roll 20 is supported on either side of the rolling station26 below the holding-down devices 56 and 58 which are arranged there.All guide rolls 20 are essentially identical; according to FIGS. 13 and14 each of them has an axle shaft 162 which is of a tubular shape in theillustrated example and is supported at either end by means of a rollerbearing 164 each on an axle journal 166 each. The axle journals 166 havea square section at their axial outer end so that they are securedagainst rotation when they are accommodated in complementary mountings168 (FIGS. 3, 5 and 6) at the machine table 16 or one of the frames 18.

The length of the axle shafts 162 is slightly larger than the width ofthe largest saw blade 10 to be processed in the machine. in order toprevent the teeth 12, which are generally set or provided with carbidetips or the like, from contacting the axle shaft 162 and to ensure thatthe saw blade 10 travelling over such an axle shaft 162 is sufficientlysupported, two or more annular rollers 170 are arranged on each axleshaft 162, which preferably consist of plastic material or hardenedsteel and which have a cylindrical surface whose diameter is larger thanthat of the axle shaft 162. At least one of the annular rollers 170arranged on the axle shaft 162 is axially adjustable so that it can bearranged in an area where it supports the saw blade 10 in the vicinityof the teeth 12 without contacting same.

According to FIG. 13 both rollers 170 shown therein are axiallyadjustable but secured against an unintentional axial adjustment in thatthey contain a spring 172 in each radial hole which forces a detent body174 radially inwards into an annular groove 176 of the axle shaft 162.In the illustrated example balls are provided as the detent bodies 174,and the annular grooves 176 have a Vee-shaped cross-section. In thismanner, each roller 170 can optionally be located in one of severalpositions which are established by the arrangement of the annulargrooves 176. The number and spacing of the annular grooves 176 areselected in such a way that a sufficiently fine-step adjustment of therollers 170 is possible.

When a saw blade 10 travels over the rollers 170, these will be causedto rotate and, due to friction, to drive the associated axle shaft 162which in turn is smoothly supported by the roller bearings 164 on theassociated axle journals 166. In the event that it is necessary toprevent an unintentional relative rotation between the rollers 170 andthe axle shaft 162 and the thereby occurring wear of the detent bodies174 and the annular grooves 176, an axis parallel longitudinal groove178 could be machined in the axle shaft 162. At the points ofintersection-between the longitudinal groove 178 and the annular grooves176 indentations will be formed into which the detent bodies 174 canenter to a greater depth than would occur in the case of mere engagementwith one of the annular grooves 176. In this manner, the rollers 170 ofthe illustrated example are secured against both a relative rotation andan axial displacement with respect to the associated axle shaft 162.Nevertheless, the rollers 170 can be released from their engagement by amoderate, externally applied force and reengaged in any other annulargroove 176.

The operation of the illustrated machine is as follows:

a) For any levelling operation to be carried out and the precedingmeasurements it is required to move the saw blade 10 in the direction ofthe arrow A--if necessary alternatingly in the opposite direction,too--and to guide it in a straight movement, i.e. to prevent or to atleast minimize a slanted travel. This is achieved by the inventivedesign of the rolling station 26, the rolls 134 and 136 of which beinginvariably responsible for the advance movement of the saw blade 10although they are pressed by the contact pressure device 138 against thesaw blade 10 only at a moderate force below the deformation limitparticularly during measuring and elimination of bulges and dents in thesaw blade. The straight movement of the saw blade 10 is monitored by oneof the measuring stations 28 along which the blade back 14 travels.

In order to monitor the straight movement, the measuring station of thethree measuring stations 28 which is arranged farthest to the right inFIGS. 1 to 6 is used, while the measuring station 28 arranged farthestto the left can be considered in this context as a fixed point for theposition of the blade back 14. With respect to the straight movement ofthe saw blade 10 it is therefore the movements of the measuring slide148, which is associated with the right measuring station 28 and abutsthe blade back 14, which are of interest. If the blade back 14 deviatesfrom its specified position in the area of the right measuring station28 this will result in an axial displacement of the rod 146 togetherwith the plate 156, which in turn causes the sensor 154 to emit signalscorresponding to the magnitude and direction of the positional deviationof the saw blade 10. The control unit 160 processes these signals--and,if desired, also the signals emitted from the remaining two measuringstations 28--to become control commands for the actuator 142 which thenswivels the roll frame 132 of the rolling station 26 about the verticalpivot axis J in either direction according to the double arrow M in FIG.2.

This means that the rolls 134 and 136 are slanted with respect to thestandard direction of travel A and thereby move the saw blade 10depending on the magnitude and direction of its determined positionaldeviation to a greater or lesser extent towards the right measuringstation 28 (FIGS. 1 to 5) or away from it. The actuator 142 will returnthe rolls 134 and 136 to their straight position no later than after thepositional deviation of the saw blade 10 in the right measuring station28 has been eliminated. In order to enable an earlier response, signalsfrom the centre station 28, which is arranged between the measuringstation 22 and the levelling station 24, can additionally be used.

b) In order to detect bulges and dents in the saw blade 10 while itperforms several cycles in the sense of the arrow A the measuring slide94 is stepped through different positions in which the sensor 106measures the saw blade 10 via several parallel tracks as usual. Themeasuring values thus obtained will be tabulated with informationconcerning the travel covered by the saw blade 10 and serve to controlthe levelling station 24 with respect to the position and magnitude ofthe impact of its rolls 120 and 122 upon the saw blade 10 in the usualmanner.

According to the invention the measuring station 22 in conjunction withthe holding-down devices 36 and 46, which are adjustable according towidth and thickness of the saw blade 10 and symmetrically with themeasuring plane B, has the additional task of measuring the stressprofile of the saw blade 10. For this purpose, a voltage is applied tothe electro-magnet 112 so that it swivels the sensor 106 to clear thesaw blade 10; the recording of the stress profile of the saw blade 10 isthe exclusive responsibility of the sensor 114. The stress profile ismade measurable according to an aspect of the invention which isindependent of (a) by operating the supporting means 48. For thispurpose, the lifting device 88 is advanced which lifts the supportingroll 86 by a distance which is predetermined by the setting of thestroke limiter 90. The saw blade 10 which is restrained to the bladesupports 32 and 42 by the two holding-down devices 36 and 46 at equaldistances on either side of the measuring plane B, i.e. which isprevented from lifting, is provided with a profile in the measuringplane B in that it is lifted by the supporting roller 86 in its centre,which depends on the magnitude and distribution of the internal stressesin the saw blade 10. This profile is measured by the sensor 114 atseveral cross-sections distributed over the length of the saw blade 10by moving the measuring slide 94 transversely over it upon standstill ofthe saw blade 10.

In accordance with the measuring results the saw blade 10 can then beprocessed in a usual manner in the rolling station 26 during thesubsequent cycles which are carried out at a generally constant speed,with the rolls 134 and 136 which are loaded by the contact pressuredevice 138 acting deformingly on the saw blade through the requirednumber of adjacent passes.

c) The way and the magnitude of the required impact of the rollingstation 26 on the saw blade 10 are also dependent on the shape of theblade back 14. Under saw mill operating conditions the saw blade 10 issubjected to greater expansion in the area of the teeth due to thecutting forces acting on the teeth 12 than in the area of the blade back14; this must therefore be expanded during levelling so that the sawblade in the area of the teeth 12 is again subjected to an increasedtensile stress when it is employed again in a sawing machine so that itdoes not wobble. A saw blade 10 travelling over the machine table 16which has a concave blade back 14 therefore generally indicates thatdeforming influences of the rolling station 26, primarily in thevicinity of the blade back 14, are required. In order to be able todetermine the location and intensity of the influence required to levelthe saw blade 10, the curvature of the blade back 14 has to be measured.This is generally done by those with skill in the art in that a straightedge is applied to the blade back 14 and the type of the requireddeformation of the saw blade is derived from the location and size ofthe light gap generated as a result.

According to the invention this task is, however, assigned to the threemeasuring stations 28, whose signals are commonly evaluated for thispurpose by taking the positions of the three measuring slides 148 whichare in contact with the blade back 14 at given distances from oneanother as coordinates of three measuring points lying on a circle. Thethree measuring points have fixed distances from each other in thedirection of travel A of the saw blade 10. Their coordinates in thisdirection are therefore fixed; only the coordinates measuredperpendicularly to the direction of travel A of the saw blade 10 in itshorizontal plane are variable. On the basis of these measurements, thecomputing and controlling unit 160 continuously determines the radius ofcurvature of the blade back 14 during one cycle of the saw blade 10 andit determines simultaneously the required adjustment of the actuator 142for the straight movement of the saw blade 10. This is an independentaspect of the invention which does not depend on the utilization of atleast one measuring station 28 for ensuring the straight movement of thesaw blade 10 as described under (a) and all the more so on themeasurement of the stress profile described under (b).

d) If a wider saw blade is to be measured and/or levelled instead of theillustrated saw blade 10, the front blade support 42 and the frontholding-down devices 46 and 58 will correspondingly be adjusted in aforward direction and, analogously, the front rollers 170 will beadjusted in a forward direction so that the saw blade which is to beprocessed now will again be supported, guided and held down in therequired manner so that the machine components involved will not contactthe teeth 12. The supporting, guiding and holding-down functions in thevicinity of the blade back 14 remain unchanged. The adjustability of thedistance of the holding-down devices 36 and 46 from the measuring planeB is another independent aspect of the invention in conjunction with thedescribed sensing of the stress profile by the measuring station 22. Thedescribed adjustability and engagement of the rollers 170 is alsoconsidered to be an independent invention.

We claim:
 1. A method of measuring and correcting the stress profile ofan elongated saw blade (10), in particular for band saws, whereinthe sawblade (10) is moved through a measuring path and a rolling path in adirection of travel (A) which essentially corresponds to itslongitudinal direction; said measuring path having a start area and anend area and a central area in between said start and end areas; twolateral edge regions of the saw blade (10) are supported on themeasuring path and held down by holding-down forces in said start areaand said end area of same; the profile of the saw blade (10) is measuredin said central area of the measuring path in a measuring plane (B)which is orthogonal to its direction of travel (A); data of the profileheight relative to a chord which extends transversely to the directionof travel (A), coordinated with data of the distance of the measuringpoints from an edge (14) of the saw blade (10) and data of the path oflongitudinal movement of the saw blade is stored; and the saw blade (10)is rolled in said rolling path in a region-by-region manner in saiddirection of travel (A) in accordance with this data, whereinsaidlateral edge regions of the saw blade (10) are retained in the startarea and the end area of the measuring path in a common reference planewhich includes the direction of travel (A) of said saw blade (10); thesaw blade (10) is lifted above the reference plane by a supporting forcewhich is exerted only in the central area of the measuring path; thestress profile developed in this manner is measured; and alternatelywith measuring and correcting of the stress profile, bulges and dents ofthe saw blade (10) are measured in the same measuring plane (B) and saidsupporting force is removed for this purpose and the saw blade (10) ismoved over the entire length of the measuring path so as to be flat inthe reference plane.
 2. The method of claim 1 wherein said supportingforce is exerted in the measuring plane (B) only.
 3. The method of claim1 wherein said supporting force is exerted only at a distance from thetwo marginal regions.
 4. A method of measuring and correcting the stressprofile of an elongated saw blade (10), in particular for band saws,whereinthe saw blade (10) is moved through a measuring path and arolling path in a direction of travel (A) which essentially correspondsto its longitudinal direction; the profile of the saw blade (10) ismeasured in a measuring plane (B) which is orthogonal to its directionof travel (A); data of the profile height relative to a chord whichextends transversely to the direction of travel (A), coordinated withdata of the distance of the measuring points from an edge (14) of thesaw blade (10) and data of the path of the longitudinal movement of thesaw blade is stored; said edge (14) of the saw blade (10) is sensed inthe plane of the saw blade orthogonally to said direction of travel (A)in order to obtain data concerning the curvatures of this edge; whereinthe saw blade (10) is rolled under an angle of up to 3° in a slanteddirection relative to its longitudinal direction in the rolling path ina region-by-region manner in the direction of travel according to allthis data, and the deviations of the saw blade (10) from a givenposition as detected at said edge (14) are corrected by rolling the sawblade in accordance with these deviations in a direction slantedrelative to its longitudinal direction.
 5. The method of claim 1 whereinsaid holding-down forces are exerted only on the marginal regions invariable, identical distances upstream and downstream the measuringplane (B) according to the width and thickness of the saw blade (10). 6.The method of claim 4 wherein said edge (14) of the saw blade (10) issensed at three places spaced in its direction of travel (A).
 7. Anapparatus for measuring and correcting the stress profile of anelongated saw blade, in particular for band saws, comprisinga machinetable (16) on which an elongated saw blade (10), in particular for aband saw, is movable in a direction (A) which essentially corresponds toits longitudinal direction; a measuring station (22) arranged at themachine table (16), said measuring station comprisinga measuring plane(B) which extends orthogonally to the direction of travel (A) and inwhich at least one sensor (106, 114) is arranged; one pair of parallelblade supports (32, 42) for one lateral edge region each of the sawblade (10); andtwo pairs of holding-down devices (36, 46) which arearranged in a start and an end zone, respectively, of the measuringstation (22) for pressing the saw blade (10) onto the blade supports(32, 42),wherein the blade supports (32, 42) lie in a common referenceplane, a supporting means (48) is arranged in the measuring plane (B),which is movable from a rest position where it does not project beyondthe measuring plane (B) into a supporting position where it lifts thesaw blade (10), and is adjustable transversely to the direction oftravel (A) of the saw blade (10); and for the purpose of adapting to sawblades (10) of different widths one of the blade supports (42) isadjustable away from or towards the other blade support (32); oneholding-down device (46) of each pair of holding-down devices (36, 46)is adjustable relative to the other holding-down device (36) in the samemanner as the associated blade support (42); and the supporting means(48) is connected with the adjustable blade support (42) and theadjustable holding-down devices (46) via a transmission (50-54) whichadjusts the supporting means (48) upon the adjustment of the bladesupport (42) and the holding-down devices (48) by a certain distance inthe same direction, but by half the distance.
 8. The apparatus of claim7 wherein the supporting means (48) is adjustable transversely to thedirection of travel (A) of the saw blade (10).
 9. The apparatusaccording to claim 7 wherein the supporting means (48) comprises asupporting roller (86) which abuts approximately in the center of thebottom of the saw blade (10).
 10. In an apparatus for measuring andcorrecting the stress profile of an elongated saw blade having a rollertrack on which an elongated saw blade (10), in particular for a bandsaw, is movable in a direction (A) which essentially corresponds to itslongitudinal direction, the improvement comprisingaxle shafts (162)which are rotatably supported and which extend over the entire width ofthe roller track and carry axially adjustable annular rollers (170)which by means of biased detent bodies (174) engage grooves (176, 178)of the associated axle shaft (162) and are thus retained in a selectedaxial position each and connected for a common rotation with the axleshaft (162).